I hadn't really ever played as Rome before- their kit seemed sort of bland to me so I always wanted to play (and re-play) other civs first. I finally got around to them recently and was pleasantly surprised. Legionnaires are actually really fun to use and have a decent learning curve that isn't apparent just from the description. Pillum (does 10 damage to adjacent enemies at the start of your turn while fortified) and cover I+II make them essentially mini citadels that you can move into enemy territory. They are really effective at moving into position and establishing a front that is hard to break while dishing damage back. I found that the ideal way to use them was to rush them into position near an enemy city and then leave them fortified to block off access to my ranged/siege. With medic I+II ranged units nearby, cover I+II, increased defense while fortified, and Pillum hitting nearby enemies they become really difficult to uproot. I found that leaving them fortified most of the time is key to their success- they aren't particularly strong when attacking like many other UUs and if you do attack you probably end up losing out on reduced damage taken AND pillum damage dished out next turn. It might be counter intuitive but I found that purposely leaving them as legionnaires and NOT upgrading them to longswordsman was best. You get a pretty miniscule CS boost as longswordsman (18 vs 22 CS) and losing Pillum on upgrade is too great a loss to justify I think. I'd even rather have a Legionnaire than a Tercio (18 vs 25 CS) as long as I can keep the legionnaire fortified most of the time but that can sometimes be tough to do so I definitely began upgrading many of my legionnaires at that point. When my gold was limited I often chose to upgrade my siege/ranged units first because legionnaires are pretty nice even eras later. The legionnaire road building ability is also surprisingly strong. It's always a good practice to build a road toward your enemy prior to starting a war to enable quicker unit cycling and reinforcements but legionnaires being able to build roads just makes that even easier. I was sometimes building 3 lane highways towards my enemy which gave crazy good mobility. It has a GPT cost, sure, but you make up for it by hardly ever losing units and speeding up your siege of the city. You can always have a worker come along later and remove unneeded roads once the conquest is complete. The road building has some synergy with the Colosseum's great general generation as well. Having extra GGs around means you can plant more citadels. Doing so near an enemy city means you can build roads even further toward it, often making your siege able to move via road to within 2 tiles and attack in a single turn. Even if you siege takes hits from enemy cities or ranged you're able to cycle your siege so quickly that the damage on the city just doesn't let up. Rome is also very well geared to largely annex their conquests. You don't destroy any buildings upon capturing a city so those cities are very quickly up to par on infrastructure and are easily able to keep up from then on thanks to the 15% production bonus as long as the capital has already constructed the building. I found myself annexing more than usual and not regretting it. Because all of your cities are typically very current on infrastructure you also tend to have less happiness problems as well. If you're like me and didn't think Rome looked all that interesting to play I would suggest giving them a try and especially sinking your teeth into using legionnaires.